Lithographic offset press plate dampening device



Jan. 13, 1959 H. P. DAHLGREN 2,868,118

LITHOGRAPHIC OFFSET PRESS PLATE DAMPENING DEVICE Filed Sept. 24. 1954 3Sheets-Sheet 1 'i "Will" i IIIIIIIIIIHIL @QM INVENTOR.

ATTCI R N EYS Jan. 13, 1959 H. P. DAHLGREN 2,868,118

LITHOGRAPHIC OFFSET PRESS PLATE DAMPEINING' DEVICE Filed Sept. 24. 19543 Sheets-Sheet 2 ATTD RN EYS Jan. 13, 1959 Filed Sept. 24. 1954 H. P.DAHLGREN 2,868,118

LITHOGRAPHIC OFFSET PRESS PLATE DAMPENING DEVICE 3 Sheets-Sheet 3 ATTD RN EVS United States Patent LITHOGRAPHIC OFFSET PRESS PLAT-E DAMPENINGDEVICE Harold P. Dahlgren, Mobile, Ala. Application September 24,1954,Serial No. 458,226

s Claims. (01. 101-147 This invention relates to lithographic offsetprinting machines, such as rotary sheet. and web fed lithographicpresses wherein the imageareas of the printing plate of the cylinder areink or grease receptive and the non-image or non-printing areas have anaflinity for moisture, and in particular, a rotary brush. spaced fromthe printing plate and not having physical contact therewith, and meansfor conveying moisture to the brush whereby upon rotation of the brushmoisture is atomized and bombarded against the surface of. the printingplate and wherein means is provided for regulating the amount ofmoisture supplied to the brush.

The purpose of this invention is to provide means for moistening thesurface of a printing plate of a lithographic offset printing machinewithout physical contact with the plate and wherein the amount ofmoisture supplied to the, plate is controlled.

In the conventional method of applying moisture to printing plates oflithographic offset printing or planegraphic printing machines, a pairof rollers covered with a fibrous or other absorbent material andsupplied with moisture by various devices are in continuous contact withthe surface of the printing plate and with continuous use of rollers ofthis type the soft surfaces become crusty and greasy and distortions ofimages of the printing plates are prevalent. With the moisture appliedcontinuously, the moisture builds up over the gap in the printing platecausing over-moistening of the leading edge of the plate: The excesswater which accumulates in the dampeningrolls must be dissipated whilethe machine is in operation or the machine must be stopped to permitsufiicient time for drying. Such rolls also deposit lint in the inkareas of the plate resulting in deterioration or wear of: the imagesofthe plates. 7

With this thought in mind, this invention contemplates an improvedmethodof supplying moisture to the printing plates of'lithographicoffset machines without physical contact of the applying means with theprinting plate, with means for withholding the moisture during passingof the gap between the ends of the plate, with means for controlling theamount of moisture supplied to the applying means andwith means foradjusting the applying means laterally to compensate for paper or othersheets of material of different sizes.

The object of this invention is, therefore, to provide meansfor applyingaproper' amount of moisture to the printing plate of a lithographicoffset printing machine without physical contact of the plate with themoisture applying means and with means for controlling the amountofmoisture supplied to laterally disposed areas of the plate.

Another object of the invention is to provide moistening means forprinting plates of lithograph offset printing machines by projecting astream of moisture against the surface of the plate whereby the moistureis applied without physical contact of the applying means.

Another important, object of the invention is to provide means forapplying moisture to printing plates of litho- 2 graphic offset printingmachines without smearing or scumming the plate.

A further object of the invention is to provide means for applyingmoisture to printing plates of lithographic offset printing machineswherein the amount of moisture supplied to the plate is controlled.

A still further object of the invention is to provide an improved meansfor supplying moisture to printing plates of lithographic offsetprinting machines without physical contact of the applying means withthe plates in which the device is of a simple and economicalconstruction.

With these and other objects and advantages in view, the inventionembodies a lithographic offset printing machine having a printing platemounted on a cylinder with conventional inking rollers, and a brushrotatably mounted parallel to the cylinder and positioned with thesurface of the brush spaced from the surface of the cylinder and inwhich means is provided for rotating the brush and also for regulatingthe amount of moisture supplied to the brush to be propelled against theplate.

Other features and advantages of the invention will appear from thefollowing description, taken in connection with the drawings, wherein:

Figure l is a plan view of a portion of a lithographic offset printingmachine showing an improved vapor producing brush positioned at one sideof the printing plate cylinder with means for rotating the brush andalso means for controllably conveying lithographic dampening solution upto the brush to be atomized and propelled against the revolving platecylinder, the intermediate part of the machine being broken away.

Figure 2 is across section through the portion of the machine shown inFigure 1 illustrating the relative positions of the moisture applyingbrush and dampening, operating and control means therefor.

Figure 3 is a longitudinal section taken on line 3-3 of Figure 2 showingthe means of connecting the control means of the brush to the eccentricmounting of the blanket or rubber cylinder.

Figure 4 is a cross section similar to that shown in Figure 2illustrating the relative positions of the moisture applying brush androller for conveying moisture up to be swept into the vapor stream.

Figure 5 is'a sectionsomewhat similar to that shown in Figure 4 showingan apron adapted to extend between the brush and moisture applyingroller for controlling the amount of moisture supplied to sections ofthe brush.

Figure 6 is a sectional plan taken on line 66 of Figure 5 showing theposition of the moisture controlling apron at one side of the machine.

'With this improved process of moistening the printing plate of alithographic offset printing machine, the liquid is projected throughspace by the springy action of the bristles of the brush in beingreleased from the moistened surface of the liquid supplying rollerwhereby the liquid 1s atomized and bombarded against or evenlydistributed over the surface of the printing plate.

Referring now to the drawings, wherein like reference characters denotecorresponding parts, the improved moistener for lithographic offsetprinting machines of this invention includes a rotary brush 10 mountedon a shaft 11, a water or other liquid supplying roller 12 positioned toextend into a tray 13, a cam 14 mounted on a shaft 15 of a cylinder 16on which a conventional printing plate 17 is mounted, a variable speedtransmission 18 for controlling the speed of the supply roller 12, ahand lever 19 for manually engaging the brush with the roller 12, whenthe blanket or rubber cylinder is in the off-impression position, and arod 20 for engaging the brush with the water supplying roller when theblanket or rubber cylinder, as indicated by the numeral 21, is in theprinting or impression position. The rod also moves the brush upwardlyout of engagement with the roller 12 as the cylinder 21 moves to theoff-impression position.

The shaft 11 of the rotary brush 10 is rotatably mounted in bearings 22and 23 in the ends of arms 24 and 25, respectively, and the arms areadjustably mounted on the ends of a shaft 26 that is mounted in framemembers 27 and 28 of the machine.

The arms 24 and which are provided with bifurcated ends are adjustablysecured to the shaft with bolts 29 and 30 which extend through extendedends thereof and which provide means for independently adjusting thepositions of the arms, thereby making it possible to adjust the ends ofthe shaft 11 so that the surface of the brush 10 may be positionedparallel to the surface of the roller 12.

The brush 10 is rotated by a Chain 31, trained over sprockets 32 and 33,and the sprocket 33 is positioned on the side of a pulley 34 whereby itis rotated by the pulley upon rotation of the pulley by a belt 35. Thebelt 35 extends to independent driving means whereby the rotary brush 10is adapted to be rotated independent of the operation of the machine.

The arms 24 and 25 are positioned to rest upon discs 36 and 37eccentrically positioned on a shaft 38 and with the shaft adapted to beactuated by the hand lever 19 or rod 20 the discs may be turned toadjust the pressure between the brush and'the roller 12 or to elevatethe brush 19 above the roller, as illustrated in Figure 2, when themachine is idling. The lever 19 is also adapted to actuate the discs 36and 37 to bring the brush 10 into contact with the supply roller 12after the machine has been idling or with the blanket or rubber cylinderin the cit-impression position in order to supply moisture to theprinting plate before the inking rollers are brought into contact withthe plate and before printing pressure is reapplied. The arms 24 and 25are urged against the surfaces of the eccentrically positioned discs 36and 37 with springs 39 and 40, the upper ends of which are attached tothe arms, as shown in Figure 4, and the lower ends of which are attachedto a rod 41 mounted in the A frame members 27 and 28.

The rod 41 is also provided With arms 42 and 43 which extend from thetray 13 and the extended ends of the arms are provided with hubs 44 and45 that are secured to the rod with set screws 46 and 47. By this meansthe position of the tray 13 is adapted to be adjusted in relation to thesupply roller 12.

As illustrated in Figure 5, the rod 41 is also adapted to be providedwith arms 48 having hubs 49 on the lower ends with thumb screws 50therein for adjusting the positions of the arms 48, and having hubs 51on the upper ends in which a rod 52 is mounted and the rod 52 providesmounting means for aprons, as indicated by the numeral 53; the apronsextending between the supply roller 12 and the brush 10 whereby with thebristles of the brush 10 contacting the roller 12 through teeth 54extended from the extended end of the apron, means is provided forregulating the area of contact between the bristles and surface of thesupply roller 12 whereby the amount of moisture supplied at the sides ofthe machine is adapted to be adjusted to compensate for the moisturedesired on the printing plate. By this means moisture may only besupplied to an area in which sheets of material are being printed or acomparatively small amount of moisture may be applied to the sides ofthe printing plate that are not being used to prevent ink from adheringthereon.

The supply roller 12 which is formed with a knurled. or roughenedsurface is mounted on a shaft 55 that is rotatably mounted in the framemembers 27 and 28 and, as illustrated in Figure 2, a gear 56 mounted onone end of the shaft 55 meshes with a gear 57 on a shaft 58 that extendsfrom the variable speed transmission 18 and on which a gear 59 thatmeshes with a gear 60 on the shaft 15 of the plate cylinder ispositioned, By this 74 of a complementary member 75.

means the speed of the moisture supply roller 12 is adjustable inrelation to the speed of the plate cylinder, this speed ratio beingcontrolled by a hand crank 61 to correspond with requirements ofdilferent jobs being performed by the machine, and the like. It will beunderstood that with this arrangement the speed ratio between supplyroller 12 and the plate cylinder will be maintained with increases anddecreases in press speed. The variable speed transmission isconventional, and it will be understood that a unit of any suitabledesign may be used. The plate cylinder 16 and the printing plate 17 realso conventional, and as illustrated in Figure 4,

1e ends of the plate are held by mounting elements 62 and 63 whereby agap 64 is provided between ends of the plate and to prevent moisturebeing supplied to the printing cylinder as the gap passes the brush 10;the brush 10 being elevated to such a position that it is spaced fromthe roller 12. The brush is actuated as a lobe 65 when the cam 14engages a roller 66 in an arm 67 on the arm 24 whereby at the time thegap is passing the brush 10 the brush is elevated to the inoperativeposition shown in Figure 2. Although the arm 67 is shown as beingattached to the arm 24 with screws 68 it is understood that the roller66 may be attached to the brush mounting elements by other suitablemeans and the cam for actuating the roller may also be of any othersuitable design.

The cam 14 is secured on the shaft 15 with clamping screws 69 and 70that are threaded in lugs 71 and 72 of the cam and that extend throughsimilar lugs 73 and It will also be understood that the cam may bemounted by other suitable means.

The positions of the discs 36 and 37 which elevate the brush areautomatically adjusted with the movement of the blanket or rubbercylinder to the idling position wherein the blanket or rubber cylinderis spaced from the plate cylinder or to the upper or printing position,by the rod 20, the lower end of which is connected to the impressionthrow on link through a collar 77, as illustrated in Figure 3. Thecollar 77 with which the blanket cylinder eccentric arm 78 is connectedto the blanket cylinder eccentric 79 is positioned between washers 80and 81 and the parts are adjustably secured to the link 76 withadjusting nuts 82 and 83.

The upper end of the rod 20 extends through an opening in a head 84 onan extension 85 of an arm 86 extended from the lower end of the lever19, and the head is resiliently held by springs 87 and 88, positioned onthe rod 20, and adjustably held by set collars 89 and 90.

Probably no other factor involved in the lithographic offset printingprocess controls or limits production and quality of work so much as theconventional dampener roller method of moistening the plate on thepress.

A study of these problems and disadvantages of the conventionaldampening system will indicate that the solution lies in a method ofconveying moisture to the plate without physical contact of the plateand the moisture source and with a more exacting and responsive overalland lateral control across the plate.

Following are listed some of the problems and disadvantages encounteredin the conventional dampening method which will be eliminated by the useof this brush type dampening method:

(1) The cost of dampener covering materials.

(2) Costly down time of press and labor necessary to change and resetdampeners when they are worn or too dirty for job or too worn and dirtyto prevent scumming of plate.

(3) The excess water which may accumulate in dampener rolls must bedissipated while running or machine must be stopped to allow sufiicienttime for drying.

(4) Dampeners must daily be run in and 16 allowed t wet up evenly.

There is the problem of lint in the inked areas of the plate, especiallyin new dampeners.

(6) Inability to get and hold exact lateral control of moisture acrossthe plate. This causes Washed out areas as well as catch-ups. Alsocauses the sticking of sheets when water slings to the delivery stackdue to excess water in certain areas.

(7) The deterioration or wear of the images and plates and thedistortion of images caused by dampener friction.

(8) The inability to get immediate increases or decreases in overallmoisture film or to vary immediately local areas.

(9) The inability to get immediate pH changes due to the reserve ofmoisture in the dampeners.

(10) The problem of over-moistening the leading edge of the plate due toa build-up of moisture in the gap.

(11) Probably more plates are lost (on the press) due to faultydampening control than any other reason.

The study of these problems and disadvantages of the conventionaldampener system will indicate that the solution lies in a method ofapplying a proper amount of moisture to the plate without physicalcontact of the plate and the source and with a method of more exactingoverall and lateral control across the plate.

It Will be understood that modifications, within the scope of theappended claims, may he made in the design and arrangement of the partswithout departing from the spirit of the invention.

What is claimed is:

1. In a printing plate moistener for a lithographic offset printingmachine having a rotatable plate cylinder with a lithographic offsetprinting plate mounted thereabout, the combination which comprises, anelongate cylindrical brush rotatably mounted on the machine in spacedparallel relationship to the exterior side of the plate; an elongateliquid retaining tray mounted on the machine and extending parallel tothe brush; a quantity of wetting liquid in said tray; an elongate liquidsupply roller rotatably mounted on the machine parallel to the brush,having one side thereof immersed in said liquid and the other sidethereof in rotative contact with the brush with the peripheral surfaceof the roller impressed into the bristles of the brush, whereby uponrelease of the bristles from the roller, as the roller and brush rotate,the liquid on the surface of said roller is atomized and projectedagainst the surface of the printing plate as the plate is rotated; andmeans to rotate the brush, roller and plate cylinder.

2. In a printing plate moistener for a lithographic offset printingmachine having a rotatable plate cylinder with a lithographic offsetprinting plate mounted thereabout, the combination which comprises, anelongate cylindrical brush rotatably mounted on the machine in spacedparallel relationship to the exterior side of the plate; an elongateliquid retaining tray mounted -on the machine and extending parallel tothe brush; a quantity of wetting liquid in said tray; an elongate liquidsupply roller rotatably mounted on the machine parallel to the brushhaving one side thereof immersed in said liquid and the other sidethereof in rotative contact with the brush with the peripheral surfaceof the roller impressed into the bristles of the brush, whereby uponrelease of the bristles from the roller, as the roller and brush rotate,the liquid on the surface of said roller is atomized and projectedagainst the surface of the printing plate as the plate is rotated; meansto rotate the brush, roller and plate cylinder; and means fortemporarily halting the supply of liquid to the brush upon passing a gapbetween the ends of the printing plate by the brush.

3. In a printing plate moistener for a lithographic offset printingmachine having a rotatable plate cylinder with a lithographic offsetprinting plate mounted there- 6 about, the combination which comprises,an elongate cylindrical brush rotatably mounted on the machine in spacedparallel relationship to the exterior side of the plate; an elongateliquid retaining tray mounted on the machine and extending parallel tothe brush; a quantity of wetting liquid in said tray; an elongate liquidsupply roller rotatably mounted on the machine parallel to the brushhaving one side thereof immersed in said liquid and the other sidethereof in rotative contact with the brush with the peripheral surfaceof the roller impressed into the bristles of the brush whereby uponrelease of the bristles from the roller, as the roller and the brushrotate, the liquid on the surface of said roller is atomized andprojected against the surface of the printing plate as the plate isrotated; means to rotate the brush, roller and plate cylinder; andadjusting means at the ends of the brush for adjusting the position ofthe brush with relation to the liquid supply roller. 1

4. In a printing plate moistener for a lithographic offset printingmachine having a rotatable plate cylinder and a lithographic offsetprinting plate mounted thereabout, the combination which comprises, anelongate cylindrical brush rotatably mounted on the machine in spacedparallel relationship to the exterior side of the plate; an elongateliquid retaining tray mounted on the machine and extending parallel tothe brush; a quantity of wetting liquid in said tray; an elongate liquidsupply roller rotatably mounted on the machine parallel to the brushhaving one side thereof immersed in said liquid and the other sidethereof in rotative contact with the brush with the peripheral surfaceof the roller impressed into the bristles of the brush whereby uponrelease of the bristles from the roller, as the roller and brush rotate,the liquid on the surface of said roller is atomized and projectedagainst the surface of the printing plate as the plate is rotated; meansto rotate the brush, roller and plate cylinder; and means for adjustingthe position of the liquid retaining tray in relation to the liquidsupply roller.

5. In a printing plate moistener for a lithographic olfset printingmachine having a rotatable plate cylinder and a lithographic offsetprint plate mounted thereabout, the combination which comprises, anelongate cylindrical brush rotatably mounted on the machine in spacedparallel relationship to the exterior side of the plate; an elongateliquid retaining tray mounted on the machine and extending parallel tothe brush; a quantity of wetting liquid in said tray; an elongate liquidsupply roller rotatably mounted on the machine parallel to the brushhaving one side thereof immersed in said liquid and the other sidethereof in rotative contact with the brush with the peripheral surfaceof the roller impressed into the bristles of the brush whereby uponrelease of the bristles from the roller, as the roller and brush rotate,the liquid on the surface of said roller is atomized and projectedagainst the surface of the printing plate as the plate is rotated; meansto rotate the brush, roller and plate cylinder; and means for actuatingthe moistener to stop the supply of liquid to the printing plate withthe machine idling, and manual actuating means for supplying moisture tothe printing plate with the machine idling.

References Cited in the file of this patent UNITED STATES PATENTS1,574,063 Cadgene et al Feb. 23, 1935 2,299,994 Kokay Oct. 27, 19422,389,730 Iler Nov. 27, 1945 2,421,824 Allen et al June 10, 19472,448,226 Marsden Aug. 31, 1948 2,672,090 Dell Mar. 16, 1954 FOREIGNPATENTS 387,694 Germany Nov. 21, 1922

